Degenerative diseases of the retina are cumulatively the most common causes of untreatable blindness. These conditions, which include age-related macular degeneration and retinitis pigmentosa, are characterized by progressive loss of cells in the outer retina. Stem cells hold great promise for treating these diseases by repopulating cells that have been lost. A cell type that will be central to the success of this strategy is the retinal pigment epithelium (RPE). Recent technological breakthroughs make possible for the first time the production of recipient-specific donor cells through reprogramming of pluripotency in adult cells and directed differentiation. However, it is not known how RPE cells produced by these and other methods compare with respect to key biological characteristics, including immunogenicity and mitochondrial senescence, when transplanted to the healthy or diseased retina. These issues are critical to the potential use of such cells for retinal disease therapy. The goal of this proposal is to study the functionality of RPE cells generated from experimentally induced pluripotent stem cells in vitro and after transplantation to the rodent or nonhuman primate retina, including their immunogenicity and their ability to rescue visual loss in a rodent model of retinal degeneration. The project will make innovative use of unique resources, including allograft and autograft stem-cell-derived rhesus monkey RPE cell lines and a naturally-occurring nonhuman primate model of macular disease. The proposal has three specific aims: 1) To generate rhesus macaque RPE cells from three sources of pluripotent stem cells--embryonic stem cells (ESCs), ESCs derived by somatic cell nuclear transfer (SCNT- ESCs), and induced pluripotent stem (iPS) cells--and evaluate their function in arresting visual decline in the RCS retinal degeneration model. 2) To investigate the immunology of these RPE cell types transplanted as allograft or autografts into the retina of adult rhesus monkeys and after retreatment of the same eye or fellow eye. 3) To characterize the differences in immune response between young and senescent rhesus monkeys, including those with age-related maculopathy which parallels intermediate human AMD. This translational research project will provide information key to the success of cell therapy in the retina. It will provide insights as to the most appropriate cell source to repopulate lost retinal cells with the aim of preserving or restoring vision, and will generate novel data on the immune response to such therapeutic intervention and the best approach to avoid graft rejection. The proposal will address these issues in an animal model with an eye and immune system that most closely resembles that of humans and in a manner closely mirroring potential clinical practice.